Molecular characterization of swine leukocyte antigen diversity in outbred pig populations.

The polymorphism of swine leukocyte antigens (SLA) has been repeatedly associated with swine immune responses, vaccine effectiveness and agricultural performance. It also has significant implications for using pigs as large animal models for biomedical research and as potential xenograft donors. Characterization of SLA genes has always been hampered by the availability of effective typing methods. Partially inbred miniature pigs with defined SLA specificities have been used extensively as animal models for various immunological studies. However, relatively few studies on swine immune response have been conducted using outbred farm pigs in part due to their poorly characterized immunogenetic backgrounds. The Meishan breed of pigs is an economically significant farm breed that is available at several research institutions in the United States. Using a DNA sequence-based typing method, the polymorphism of SLA genes was characterized in the breeding stock of a resource population of Meishan pigs. A simple SLA typing assay using polymerase chain reaction with sequence-specific primers (PCR-SSP) was then developed to rapidly determine the SLA types in the pigs from this herd. The results provide a foundation for the establishment of SLA-defined farm pig lines which will be valuable experimental models for agricultural research. To further facilitate the study of SLA influence and promote the use of swine with different immunogenetic backgrounds as animal models, low-resolution SLA typing assays were developed for characterizing the SLA class I and class II genes in outbred pigs using the PCR-SSP method. Recent establishment of a SLA nomenclature system has assigned alleles into groups based on DNA sequence similarities. PCR primers were therefore designed to distinguish each of the alleles by group definitions based upon shared polymorphic sequence motifs. These assays were then used to obtain SLA class I and class II haplotype information and determine the extent of SLA diversity in four outbred populations of conventional farm pig totaling 394 individuals. This approach not only facilitates the study of genetic diversity in outbred pig populations, it also provides the means for further understanding the role of SLA genes to advance biomedical science and to improve animal health.